Re: [PATCH] mm: Introduce GFP_PGTABLE

[Christophe Leroy]

Le 12/01/2019 Ã 13:12, Matthew Wilcox a ÃcritÂ:
> On Sat, Jan 12, 2019 at 03:56:38PM +0530, Anshuman Khandual wrote:
> > All architectures have been defining their own PGALLOC_GFP as (GFP_KERNEL |
> > __GFP_ZERO) and using it for allocating page table pages.
>
> Except that's not true.
>
> > +++ b/arch/x86/mm/pgtable.c
> > @@ -13,19 +13,17 @@ phys_addr_t physical_mask __ro_after_init = (1ULL << __PHYSICAL_MASK_SHIFT) - 1;
> >   EXPORT_SYMBOL(physical_mask);
> >   #endif
> >   
> > -#define PGALLOC_GFP (GFP_KERNEL_ACCOUNT | __GFP_ZERO)
> > -
> >   #ifdef CONFIG_HIGHPTE
>
> ...
>
> >   pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
> >   {
> > -	return (pte_t *)__get_free_page(PGALLOC_GFP & ~__GFP_ACCOUNT);
> > +	return (pte_t *)__get_free_page(GFP_PGTABLE & ~__GFP_ACCOUNT);
> >   }

As far as I can see,

#define GFP_KERNEL_ACCOUNT (GFP_KERNEL | __GFP_ACCOUNT)

So what's the difference between:

(GFP_KERNEL_ACCOUNT | __GFP_ZERO) & ~__GFP_ACCOUNT

and

(GFP_KERNEL | __GFP_ZERO) & ~__GFP_ACCOUNT

Christophe

> I think x86 was the only odd one out here, but you'll need to try again ...